1. Field of the Invention
The present invention relates to video cassette recorders (VCR's) and, more particularly, to programming VCR's for unattended recording.
2. Description of Prior Art
Programming a VCR for unattended recording requires a user to follow a step-by-step procedure that is confusing and error prone. In particular, the detailed process of entering a start time, channel, date, length, and so forth prevents most users from learning how to program a VCR. As a result, the vast majority of VCR's cannot be used by their owners for unattended recording.
One of the earliest attempts at simplifying VCR programming is bar-code scan programming, as taught by Kihara et al., U.S. Pat. No. 4,475,153. The technique, however, has;
distinct disadvantages. For example, publishing a bar code for each TV listing proved to be a difficult task, due in large part to the increased complexity and size requirements. As a result, bar-encoded TV guides never became widely available. Without bar-encoded TV guides, users must follow a detailed procedure--scanning a start time, channel, date, and length from a pre-printed card. To date, there has been little interest in bar-code programming techniques.
There have been other attempts as well. A recording scheme based on the concurrent transmission of a program identifier is described by Breese in UK Patent Application GB 2 126 002 A. Similar techniques are described by others, e.g., Kruger et al. in U.S. Pat. No. 4,488,179. The program identifier is based on program codes available from media sources, such as teletext broadcasts and printed guides. More recently, U.S. Pat. No. 4,706,121 to Young discloses a "point-and-shoot" programming method which combines the input of schedule information with remote control of a programming apparatus.
Other attempts have been made at simplifying TV viewing and recording. For example, U.S. Pat. No. 4,755,883 to Uehira describes a removable input device for an electronic recording apparatus; U.S. Pat. No. 4,488,179 to Kruger et al. describes a TV viewing center having two tuners, one for a TV signal, the other for supplementary information; and U.S. Pat. No. 4,703,359 to Rumbolt et al. describes a universal remote control unit with model identification capability, the control including a learn mode.
The disclosures of each of the foregoing references are hereby incorporated by reference.
Perhaps the best-known program code programming scheme in the U.S. is a variation taught by Yuen et al., WO Application 90/07844. In the system of Yuen, a proprietary algorithm is used to compress start time, date, program length, and channel information into a multi-digit number, i.e., a compressed code. Specifically, Yuen employs a time-dependent recording method where a recording starts when a selected program schedule and a clock timer coincide. In the concurrent transmission scheme of Breese, in contrast, a recording commences when a concurrently transmitted program ID matches a selected program schedule or code.
The compressed codes of Yuen varying in lengths depending on the "priority" of a listing. High priority programs, such as primetime shows on popular channels, are assigned short codes. For example, a system which accommodates 128 channels, 31 day period, 48 half-hour start times, and 16 length selections requires seven digit to encode a total of 3,047,424 combinations. With compression, however, high priority listings can be represented in as few as two digits.
The compression technique of Yuen maps popular broadcasters to high priority numbers. For example, CBS may be mapped to the highest priority number of 0, NBC to 1, ABC to 2, and the like. Less popular broadcasters, on the other hand, are given low priority numbers, e.g., 131. Popular viewing times ("primetime") are also accorded high priority. For example, a start time of 6 p.m. may be mapped to the number 0, 6:30 p.m. mapped to 1, 7 p.m. mapped to 2; 4:15 a.m., on the other hand, is accorded a low priority number of 48. Program lengths are similarly mapped. For example, one-half hour is mapped to 0, 1 hours is mapped to 1, and so forth; 5 hours and 30 minutes, a low priority length, may be mapped to 16.
Dates, however, are not prioritized but require two digits for any day up to thirty-one days. Thus a program code is generated by simply combining the priority numbers for channel, start time, link, and date to form a multi-digit number. For a television program on CBS, a 6 p.m. start time, a program length of 30 minutes, and a date of the eleventh, the resulting compression code would be 0+0+11 or simply 11 (since leading zeroes are ignored). The disclosure of Yuen et al. is hereby incorporated by reference.
While the system of Yuen represents an improvement over prior techniques, the system has several shortcomings. In particular, the compressed codes create significant new problems. One problem, for example, is the "ballooning" of codes. While the average length of printed compressed codes can be held to about 6 digits, low priority program codes often dramatically increase or "balloon up" to more than twice the nominal digits, at times exceeding 20 digits. These codes, like barcodes, are difficult and expensive to publish. As a result, publishers often omit lower priority codes in order to conserve print space and minimize clutter. Thus, the system of Yuen provides a simplified programming scheme at the expense of viewers who watch "low priority" programs.
Due to the proprietary algorithm employed by Yuen, the compressed codes cannot be duplicated or improvised by the user. If a code is unavailable for a TV program, e.g., it has been omitted by the publisher or the TV program has been re-scheduled, the user must manually enter the TV program into the VCR or forego recording it altogether.
The varying lengths of the compressed codes create additional problems. With wildly varying lengths, the compressed codes are prone to transcription errors by publishers as well as VCR users. Furthermore, adjacent compressed codes can be very dissimilar and, thus, verification (e.g., digit count checking or adjacent codes comparison) is not readily available. While the system of Yuen can generate compact codes for TV listings, it also has many undesirable features which limit its usefulness.
Thus, it is desirable to have a system and methods which permits any user to program a VCR for unattended recording of any program regardless of priority. Furthermore, the system should not require pre-generated codes of varying or excessive lengths. The present invention fulfills these and other needs.